Alternator size

[chargd72]

I'm currently running a 78 amp alt but I'm getting a drain due to all the after market electrical components.  I'm running a Mallory Hyfire boost proportionate ignition box, Aeromotive A1000 fuel pump, '95 Ford Taurus electric fan with variable speed controller, after market stereo, digital boost gauge, digital wideband gauge all with the typical components it takes to run.  I did a few things to help reduce load like HID headlights and LED tail light and side markers.  At idle, I know my 78 amp alt just won't keep up.  I'm thinking of going to a D300 120 amp alt but I'd like to hear what you guys think.

[Dino]

Go for it.  Cheap and easy upgrade and by the looks of it, one you need.  120 should suffice although there's nothing wrong getting one a bit bigger.  The car will only use the juice it needs.  Check Mancini Racing for their bolt in Denso kits.

[John_Kunkel]

And, of course, increase the wire size to match the 120-amp unit and consider bypassing the ammeter.

[flyinlow]

I run 100 amp single wire alternators on both Chargers. Works well. Larger charging wire with a 100 amp Maxi fuse in it. Amp meter is bypassed.

Two concerns;  a short circuit ( that's what the fuse is for)  and a dead battery. You jump start the car and the alt. goes full blast to recharge the battery sending 100 amps thru your 40 year old wiring that was never built for that current level. I run the new charging wire with fuse to the starter relay terminal. Amp meter does not read correctly after this. Also use relays to power headlights, fans, etc. and keep the higher currents outside of the cab.

[chargd72]

I ended up ordering a 114 amp unit for a W300.  I already have parallel lines running from alt to starter relay, and new parallel lines running from the relay to the battery since it has extra distance to travel to get to the trunk.  I think this should do the trick.

[Jaysick]

Im running a 100amp and have pretty much everything you listed minus the fuel pump.  Dual fans and stereo system 750w amp and with everything running, headlights fan stereo brake lights, it doesnt drop below 12.5 when sitting idle.  If all those things are on (minus the brake lights) while driving even just a little peddle it goes up to 14.